Efficient system and method for generating an audio beacon

ABSTRACT

An audio emission device and an audio capture device that may respectively emit and capture sound within a listening area is described. The audio emission device may produce one or more primary audio beams in the listening area. Each of the primary audio beams may be formed by weighting a set of modal beam patterns. Separate orthogonal test signals may be injected into each modal beam pattern. Based on these separate orthogonal test signals, the individual modal beam patterns may be extracted from a detected sound signal, produced by the audio capture device, such that the contribution from each of these modal patterns in the detected sound signal may be determined. Utilizing the contributions from each modal beam pattern in the detected sound signal, the spatial relationship (e.g., distance and/or orientation/angle) between the audio emission device and the audio capture device may be determined.

FIELD

This non-provisional application claims the benefit of the earlierfiling date of U.S. Provisional Application No. 62/105,671 filed Jan.20, 2015.

FIELD

An embodiment of the invention relates to generating audio beacons thatmay then used to for example determine the relative location andorientation of an audio emission device. Other embodiments are alsodescribed.

BACKGROUND

It is often useful to know the location/orientation of an audio capturedevice (e.g., a microphone array) relative to an audio emission device(e.g., a loudspeaker array). For example, this location/orientationinformation may be utilized for optimizing audio-visual content renderedby a computing device. Traditionally, location information may bedetermined using a set of audio beacons produced by the audio emissiondevice and detected by the audio capture device. For example, an audioemission device may emit a set of beacon beams along with a set ofintended/primary beams. The primary beams may represent channels for apiece of sound program content (e.g., a musical composition or asoundtrack for a movie) while the beacon beams are purely intended to bedetected by the audio capture device for determining the spatialrelationship between the audio capture device and the audio emissiondevice.

However, the approach discussed above suffers from inefficiencies asbeacon beams are separate and distinct from primary beams. Accordingly,extra processing overhead must be incurred by the audio emission deviceto produce these beacon beams.

The approaches described in this section are approaches that could bepursued, but not necessarily approaches that have been previouslyconceived or pursued. Therefore, unless otherwise indicated, it shouldnot be assumed that any of the approaches described in this sectionqualify as prior art merely by virtue of their inclusion in thissection.

SUMMARY

An audio emission device and an audio capture device that mayrespectively emit and capture sound, within a listening area aredescribed. In particular, the audio emission device may include aloudspeaker array, including a set of transducers, for emitting soundand the audio capture device may include one or more microphones (e.g.,a standalone microphone, or a set of microphones in a microphone array)for capturing sound in a listening area.

Orthogonal test signals may be added into a set of modal sound patternsproduced by the audio emission device, wherein the modal sound patternsare also weighted to produce a set of primary audio beams. The modalsound patterns may be extracted from sounds detected by the audiocapture device based on the injected orthogonal test signals, such thatthe modal beam patterns operate as audio beacons.

In one embodiment, the audio emission device may produce a set of one ormore primary audio beams in the listening area. Each of the primaryaudio beams may be formed by weighting a set of modal beam patterns. Inone embodiment, separate orthogonal test signals may be injected intoeach modal beam pattern. Based on these separate orthogonal testsignals, the individual modal beam patterns may be extracted from adetected sound signal produced by the audio capture device such that thecontribution from each of these modal patterns in the detected soundsignal may be determined. Utilizing the contributions from each modalbeam pattern in the detected sound signal, the spatial relationship(e.g., distance and/or orientation/angle) between the audio emissiondevice and the audio capture device may be determined. Accordingly, themodal beam patterns, which are used to generate the primary beams, mayalso be used as audio beacons.

As discussed above, by injecting orthogonal test signals into modal beampatterns, which are used to generate primary audio beams, the modal beampatterns may function as audio beacons. Accordingly, audio beacons thatare separate from the primary audio beams do not need to be generated asinstead the modal beam patterns that form the primary audio beams may beused as audio beacons for determining the relative position of the audioemission device relative to the audio capture device.

The above summary does not include an exhaustive list of all aspects ofthe present invention. It is contemplated that the invention includesall systems and methods that can be practiced from all suitablecombinations of the various aspects summarized above, as well as thosedisclosed in the Detailed Description below and particularly pointed outin the claims filed with the application. Such combinations haveparticular advantages not specifically recited in the above summary.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention are illustrated by way of example andnot by way of limitation in the figures of the accompanying drawings inwhich like references indicate similar elements. It should be noted thatreferences to “an” or “one” embodiment of the invention in thisdisclosure are not necessarily to the same embodiment, and they mean atleast one.

FIG. 1 shows an audio emission device and an audio capture device thatmay respectively emit and capture sound within a listening areaaccording to one embodiment.

FIG. 2 shows a component diagram of the audio emission device accordingto one embodiment.

FIG. 3 shows a side perspective view of the audio emission deviceaccording to one embodiment.

FIG. 4 shows a component diagram of the audio capture device accordingto one embodiment.

FIG. 5 shows a method according to one embodiment for adding orthogonaltest signals into a set of modal beam patterns produced by the audioemission device, wherein the modal beam patterns are weighted to producea set of primary audio beams.

FIG. 6 shows digital signal processing components used for addingorthogonal test signals into a set of modal beam patterns that areproduced by the audio emission device, wherein the modal beam patternsare weighted to produce a set of primary audio beams.

FIG. 7A shows an omnidirectional modal beam pattern according to oneembodiment.

FIG. 7B shows a vertical dipole modal beam pattern according to oneembodiment.

FIG. 7C shows a horizontal dipole modal beam pattern according to oneembodiment.

FIG. 8A shows a cardioid beam pattern pointed in a first direction basedon a first set of weights applied to a set of modal patterns accordingto one embodiment.

FIG. 8B shows a cardioid beam pattern pointed in a second directionbased on a second set of weights applied to a set of modal patternsaccording to one embodiment.

FIG. 8C shows a cardioid beam pattern pointed in a third direction basedon a third set of weights applied to a set of modal patterns accordingto one embodiment.

FIG. 9 shows a determined angle and distance between the audio emissiondevice and the audio capture device according to one embodiment.

DETAILED DESCRIPTION

Several embodiments are described with reference to the appendeddrawings. While numerous details are set forth, it is understood thatsome embodiments of the invention may be practiced without thesedetails. In other instances, well-known circuits, structures, andtechniques have not been shown in detail so as not to obscure theunderstanding of this description.

FIG. 1 shows an audio emission device 101A and an audio capture device101B that may respectively emit and capture sound within a listeningarea 103. In particular, the audio emission device 101A may include aloudspeaker array 105, including a set of transducers 107, for emittingsound and the audio capture device 101B may include one or moremicrophones 109 (e.g., a standalone microphone 109, or a set ofmicrophones 109 in a microphone array 111) for capturing sound.

As will be described in greater detail below, the audio emission device101A may produce a set of primary audio beams in the listening area 103.Each of the primary audio beams may be formed by weighting a set ofmodal beam patterns. In one embodiment, separate orthogonal test signalsmay be injected into each modal beam pattern. Based on these separateorthogonal test signals, the individual modal beam patterns may beextracted from a detected sound signal produced by the audio capturedevice 101B such that the contribution from each of these modal patternsin the detected sound signal may be determined. Utilizing thecontributions from each modal beam pattern in the detected sound signal,the spatial relationship (e.g., distance and orientation/angle) betweenthe audio emission device 101A and the audio capture device 101B may bedetermined. Accordingly, as will be described in greater detail below,the modal beam patterns, which are used to generate the primary beams,may also be used as audio beacons for determining the spatialrelationships between the audio emission device 101A and the audiocapture device 101B.

As shown in FIG. 1, the audio devices 101A/101B may be located in alistening area 103. The listening area 103 may be a room of any sizewithin a house, a commercial establishment, or any other structure. Forexample, the listening area 103 may be a home office of a user/listener.

FIG. 2 shows a component diagram of the audio emission device 101Aaccording to one embodiment. The audio emission device 101A may be anycomputing system that is capable of emitting sound into the listeningarea 103. For example, the audio emission device 101A may be a laptopcomputer, a desktop computer, a tablet computer, a video conferencingphone, a set-top box, a multimedia player, a gaming system, and/or amobile device (e.g., cellular telephone or mobile media player). Eachelement of the audio emission device 101A shown in FIG. 2 will now bedescribed.

The audio emission device 101A may include a main system processor 201and a memory unit 203. The processor 201 and memory unit 203 aregenerically used here to refer to any suitable combination ofprogrammable data processing components and data storage that conductthe operations needed to implement the various functions and operationsof the audio emission device 101A. The processor 201 may be a specialpurpose processor such as an application-specific integrated circuit(ASIC), a general purpose microprocessor, a field-programmable gatearray (FPGA), a digital signal controller, or a set of hardware logicstructures (e.g., filters, arithmetic logic units, and dedicated statemachines) while the memory unit 203 may refer to microelectronic,non-volatile random access memory. An operating system may be stored inthe memory unit 203, along with application programs specific to thevarious functions of the audio emission device 101A, which are to be runor executed by the processor 201 to perform the various functions of theaudio emission device 101A. For example, the memory unit 203 may includea beam emission unit 205, which in conjunction with other hardware andsoftware elements of the audio emission device 101A, emits a set ofmodal beam patterns into the listening area 103. As will be described infurther detail below, these modal beam patterns (1) may be used forconstructing one or more primary beam patterns where each primary beampattern may be assigned, via beam input parameters, to a separate one ormore channels of sound program content (e.g., each input channel of thesound program content may be assigned a separate primary beam, and theprimary beam is decomposed into contributions from the modal beams) and(2) may be used as audio beacons for determining the spatialrelationship between the audio capture device 101B and the audioemission device 101A.

As noted above, in one embodiment, the audio emission device 101A mayinclude a loudspeaker array 105 for outputting sound into the listeningarea 103. As shown in FIG. 1 and FIG. 2, the loudspeaker array 105 mayinclude multiple transducers 107 housed in a single cabinet. In theexample shown in FIG. 2, the loudspeaker array 105 has ten distincttransducers 107 evenly aligned within a cabinet. Although shown in FIG.2 as aligned in a flat plane or a straight line, the transducers 107 maybe aligned in a curved fashion along an arc. For example, in oneembodiment, the transducers 107 may be uniformly integrated on the faceof a cylindrical cabinet as shown in the overhead view of the audioemission device 101A in FIG. 1 and the side view of the audio emissiondevice 101A shown in FIG. 3. In other embodiments, different numbers oftransducers 107 may be used with uniform or non-uniform spacing andalignment.

The transducers 107 may be any combination of full-range drivers,mid-range drivers, subwoofers, woofers, and tweeters. Each of thetransducers 107 may use a lightweight diaphragm, or cone, connected to arigid basket, or frame, via a flexible suspension that constrains a coilof wire (e.g., a voice coil) to move axially through a cylindricalmagnetic gap. When an electrical audio signal is applied to the voicecoil, a magnetic field is created by the electric current in the voicecoil, making it a variable electromagnet. The coil and the transducers'107 magnetic system interact, generating a mechanical force that causesthe coil (and thus, the attached cone) to move back and forth, therebyreproducing sound under the control of the applied electrical audiosignal coming from a source.

Each transducer 107 may be individually and separately driven to producesound in response to a separate and discrete audio signals. By allowingthe transducers 107 in the loudspeaker array 105 to be individually andseparately driven according to different parameters and settings(including individual drive signal filters, which control delays,amplitude variations, and phase variations across the audio frequencyrange), the loudspeaker array 105 may produce numerous directivitypatterns to simulate or better represent respective channels of soundprogram content. For example, the transducers 107 in the loudspeakerarray 105 may be individually driven to produce a set of modal beampatterns as will be described in greater detail below.

In one embodiment, the audio emission device 101A may include acommunications interface 207 for communicating with other componentsover one or more connections. For example, the communications interface207 may be capable of communicating using Bluetooth, the IEEE 802.11xsuite of standards, IEEE 802.3, cellular Global System for MobileCommunications (GSM) standards, cellular Code Division Multiple Access(CDMA) standards, and/or Long Term Evolution (LTE) standards. In oneembodiment, the communications interface 207 facilitates thetransmission/reception of video, audio, and/or other pieces of data.

Turning now to FIG. 4, the audio capture device 101B will be described.The audio capture device 101B may be any computing system that iscapable of detecting/recording sound in the listening area 103. Forexample, the audio capture device 101B may be a laptop computer, adesktop computer, a tablet computer, a video conferencing phone, aset-top box, a multimedia player, a gaming system, and/or a mobiledevice (e.g., cellular telephone or mobile media player).

The audio capture device 101B may include a main system processor 401and a memory unit 403. Similar to the processor 201 and the memory unit203, the processor 401 and the memory unit 403 are generically used hereto refer to any suitable combination of programmable data processingcomponents and data storage that conduct the operations needed toimplement the various functions and operations of the audio capturedevice 101B. The processor 401 may be a special purpose processor suchas an ASIC, a general purpose microprocessor, a FPGA, a digital signalcontroller, or a set of hardware logic structures (e.g., filters,arithmetic logic units, and dedicated state machines) while the memoryunit 403 may refer to microelectronic, non-volatile random accessmemory. An operating system may be stored in the memory unit 403, alongwith application programs specific to the various functions of the audiocapture device 101B, which are to be run or executed by the processor401 to perform the various functions of the audio capture device 101B.For example, the memory unit 403 may include a sound detection unit 405and an orientation determination unit 407. These units 405 and 407, inconjunction with other hardware and software elements of the audiocapture device 101B, (1) detect/measure sounds in the listening area 103(e.g., containing modal beam patterns produced by the audio emissiondevice 101A), (2) extract/separate each of the modal beam patternsrepresented in a detected sound signal based on detected orthogonal testsignals that had been injected into each modal pattern, and (3)determine the orientation of the audio capture device 101B in relationto the audio emission device 101A based on these modal sound patterns.

As noted above, in one embodiment, the audio capture device 101B mayinclude one or more microphones 109. For example, the audio capturedevice 101B may include multiple microphones 109 arranged in amicrophone array 111. Each of the microphones 109 in the audio capturedevice 101B may sense sounds and convert these sensed sounds intoelectrical signals. The microphones 109 may be any type ofacoustic-to-electric transducer or sensor, including aMicroElectrical-Mechanical System (MEMS) microphone, a piezoelectricmicrophone, an electret condenser microphone, or a dynamic microphone.The microphones 109 may be used with various filters that can controlgain and phase across a range of frequencies in the audible spectrum(including possible use of delays) to provide a range of polar patterns,such as cardioid, omnidirectional, and figure-eight. The generatedpolar, sound pickup patterns alter the direction and area of soundcaptured in the vicinity of the audio capture device 101B. In oneembodiment, the polar patterns of the microphones 109 may varycontinuously over time.

In one embodiment, the audio capture device 101B may include acommunications interface 413 for communicating with other componentsover one or more connections. For example, similar to the communicationsinterface 207, the communications interface 413 may be capable ofcommunicating using Bluetooth, the IEEE 802.11x suite of standards, IEEE802.3, cellular GSM standards, cellular CDMA standards, and/or LTEstandards. In one embodiment, the communications interface 413facilitates the transmission/reception of video, audio, and/or otherpieces of data over one or more connections.

Turning now to FIG. 5, a method 500 will be described for addingorthogonal test signals into a set of modal beam patterns produced bythe audio emission device 101A, wherein the modal beam patterns are alsoweighted and combined to produce a set of primary audio beams. The modalbeam patterns may then be extracted from sounds detected by the audiocapture device 101B, based on the injected orthogonal test signals, suchthat the modal beam patterns operate as audio beacons. The modal beampatterns, which operate as audio beacons based on injected orthogonaltest signals, may be used for determining the spatial relationship(e.g., distance and orientation/angle) between the audio emission device101A and the audio capture device 101B.

Each operation of the method 500 may be performed by one or morecomponents of the audio emission device 101A, the audio capture device101B, and/or another device. For example, one or more of the beamemission unit 205 of the audio emission device 101A and/or the sounddetection unit 405 and the orientation determination unit 407 of theaudio capture device 101B may be used for performing the variousoperations of the method 500. Although the units 205, 405, and 407 aredescribed as software or instructions residing in the memory units 203and 403, respectively, to be executed by the processors 201, 401, inother embodiments, the actions of the processors 201, 401 executing theunits 205, 405, and 407 may be implemented by one or more hardwiredlogic structures, including digital filters, arithmetic logic units, anddedicated state machines.

The method 500 will be described in relation to the components shown inFIG. 6. In one embodiment, the components shown in FIG. 6 may beintegrated within or otherwise represented by one or more of the units205, 405, and 407.

Although the operations of the method 500 are shown and described in aparticular order, in other embodiments the operations of the method 500may be performed in a different order. For example, one or more of theoperations may be performed concurrently or during overlapping timeperiods. Each operation of the method 500 will now be described below byway of example.

In one embodiment, the method 500 may commence at operation 501 with thereceipt of a set of audio signals representing one or more channels fora piece of sound program content. For instance, the audio emissiondevice 101A may receive N channels of audio, as shown in FIG. 6,corresponding to a piece of sound program content (e.g., a musicalcomposition or a soundtrack of a movie). For example, the channelsreceived at operation 501 may correspond to left and right audiochannels of a movie soundtrack, where in that case N=2. The audiosignals/channels may be received at operation 501 from an externalsystem or device (e.g., an external computer or streaming audio service)via the communications interface 207. In other embodiments, the audiosignals/channels may be stored locally on the audio emission device 101A(e.g., stored in the memory unit 203) and retrieved at operation 501.

At operation 503, the one or more audio channels may be processed usingone or more filters. For example, as shown in FIG. 6, each of the Naudio channels may be processed by a corresponding one of Finite ImpulseResponse (FIR) filters 601 ₁-601 _(N) that compose an input filter bank.The FIR filters 601 ₁-601 _(N) may be selected or configured based oncharacteristics of the listening area 103 and or characteristics of thechannels themselves. For example, the FIR filters 601 ₁-601 _(N) mayprocess individual frequency components of the N channels to increase ordecrease reverberation of the N channels during playback within thelistening area 103.

At operation 505, one or more beam inputs may be received describingdesired characteristics for N primary beams that will be used forplaying back the N channels, respectively. In other words, each primarybeam is assigned to play back a separate one of the N input channels.For example, as shown in FIG. 6, the inputs received at operation 505may include (1) beam type (e.g., a cardioid beam, a hypercardioid beam,a third order beam, etc.) and (2) beam angle (e.g., 0°-360°), for eachprimary beam. As an example, in the case of an audio program having onlytwo channels (left and right), there may be two primary beams defined bythe beam inputs, one for the left channel and one for the right. Thebeam inputs may be received at operation 505 from any source. Forexample, the beam inputs may be received from a user indicating theirpreferences for sound emitted in the listening area 103, or from anaudio engineer configuring the audio emission device 101A in alaboratory or manufacturing facility. In other embodiments, the beaminputs may be automatically derived by the audio emission device 101Abased on characteristics of the listening area 103 (e.g., size of thelistening area 103 and/or the location of walls, ceiling, and floor inthe listening area 103) and/or characteristics of the N channels (e.g.,type of sound program content represented by the N channels, such as anaction movie, or a recording of a musical concert).

The N audio channels may be represented in a matrix or a similar datastructure. For example, samples from the N audio channels that have beenprocessed by the FIR filters 601 ₁-601 _(N) may be represented by theaudio sample matrix X:

$X = \begin{bmatrix}x_{1} \\\vdots \\x_{N}\end{bmatrix}$

In the example audio sample matrix X, each component or value x_(i)represents a discrete time division of audio channel i. In oneembodiment, at operation 507 the audio matrix X may be processed (basedon beam inputs received at operation 505) by a beam pattern matrixmixing unit 603, to produce a modal gain matrix. The modal gain matrixmay be viewed as representing a number of weighted modal beam patterns.The beam pattern mixing unit 603 may regulate the shape and direction ofbeam patterns for each of the N audio channels, in view of the beaminputs received at operation 505 which describe desired characteristicsfor N primary beams. The primary beams as defined by the beam inputs (orbeam input patterns) characterize how sound radiates from thetransducers 107 in the loudspeaker array 105 and into the listening area103 (once the transducers 107 are driven by their respective drivesignals that have been generated in accordance with the primary beams).For example, a highly directed cardioid beam pattern (having highdirectivity index, DI) may emit a high degree of sound directly at alistener or another specified area while emitting relatively loweramounts of sound into other areas of the listening area 103, in general.In contrast, a lower directed beam pattern (having low DI, e.g., anomnidirectional beam pattern) may emit a more uniform amount of soundthroughout the listening area 103 without special attention to alistener or any specified area.

For a loudspeaker array 105 with transducers 107 arranged in a circular,cylindrical, spherical, or otherwise curved manner, the radiation ofsound may be represented by a set of frequency invariant beam patternmodes or bases. The beam pattern mixing unit 603 may represent or definea desired primary beam pattern in terms of (or as a weighted combinationof) a set of two or more predefined, modal beam patterns. For instance,the predefined modal beam patterns may include an omnidirectionalpattern (FIG. 7A), a vertical dipole pattern (FIG. 7B), and a horizontaldipole pattern (FIG. 7C). For the omnidirectional pattern, sound isequally radiated in all directions relative to the outputtingloudspeaker array 105. For the vertical dipole pattern, sound isradiated in opposite directions along a vertical axis and symmetricalabout a horizontal axis. For the horizontal dipole pattern, sound isradiated in opposite directions along the horizontal axis andsymmetrical about the vertical axis. Although described as includingomnidirectional, vertical dipole, and horizontal dipole modal beampatterns, in other embodiments the predefined modal beam patterns mayinclude additional patterns, including higher order beam patterns. Aswill be used herein, M modal beam patterns that are each orthogonal toeach other may be used. In some embodiments, M may be defined in termsof the beam composition order S as shown below:M=2S+1

The beam pattern mixing unit 603 may define a set of weighting valuesfor each of the N audio channels and each of the M predefined modal beampatterns. The weighting values define the amount of each of the Nchannels to apply to each of the M modal beam patterns, such that adesired, corresponding primary beam pattern, e.g., a separate primarybeam for each of the N channels, may be generated by the loudspeakerarray 105. In other words, the primary beam pattern is given as acombination of the so-weighted, M modal beam patterns. For example,through the setting of corresponding weighting values, anomnidirectional modal beam pattern may be mixed with a horizontal dipolemodal beam pattern to yield a cardioid beam pattern directed at 90° asshown in FIG. 8A. In another example, through the setting ofcorresponding weighting values, an omnidirectional modal beam patternmay be mixed with a vertical dipole modal beam pattern to yield acardioid pattern directed at 0° as shown in FIG. 8B. As shown anddescribed, the combination or mixing of the predefined modal beampatterns may produce beam patterns with different shapes and directionsfor separate audio channels. Accordingly, the beam pattern mixing unit603 may define a first set of weighting values for a first audio channelsuch that the loudspeaker array 105 may be driven to produce a firstprimary beam pattern, while the beam pattern mixing unit 603 may alsodefine a second set of weighting values for a second channel such thatthe loudspeaker array 105 may be driven to produce a second primary beampattern.

In one embodiment, the resulting combination of the predefined modalbeam patterns may be non-proportional such that more of one modal beampattern may be used in comparison to another modal beam pattern, toproduce a desired beam pattern for an audio channel. In someembodiments, the weighting values defined by the beam pattern mixingunit 603 may be represented by any real numbers. For example, weightingvalues of

$\frac{1}{\sqrt{2}}$may be separately applied to a horizontal dipole modal beam pattern anda vertical dipole modal beam pattern, while a weighting value of one isapplied to an omnidirectional modal beam pattern. The mixing of thesethree variably weighted modal beam patterns may yield a cardioid primarybeam pattern directed at 270° as shown in FIG. 8C. Applying differentproportions/weights of various modal beam patterns allows the generationof numerous possible primary beam patterns, far in excess of the numberof direct combinations of the predefined modal beam patterns.

As described above, different weighting values may be used to applydifferent levels of each predefined modal beam pattern to generate adesired primary beam pattern, for a corresponding audio channel. In oneembodiment, the beam pattern mixing unit 603 may use a beam patternmatrix Z that defines a primary beam pattern for each of the N audiochannels in terms of weighting values applied to the predefined M modalbeam patterns. For example, each entry a in the beam pattern matrix Zmay correspond to a real number weighting value for a predefined modalbeam pattern and a corresponding audio channel. For a set of M modalpatterns and N audio channels, the beam pattern matrix Z_(M,N) may berepresented as:

$Z_{M,N} = \begin{bmatrix}\alpha_{1,1} & \ldots & \alpha_{1,N} \\\vdots & \ddots & \vdots \\\alpha_{M,1} & \ldots & \alpha_{M,N}\end{bmatrix}$

As previously described, each of the weighting values α represents thelevel or degree a predefined modal beam pattern is to be applied to acorresponding audio channel. In the above example matrix Z_(M,N), eachcolumn represents the level or degree to which a respective one of the Mpredefined modal beam patterns will be applied, to a corresponding audiochannel in the N received/retrieved audio channels. Each of theweighting values α may be based on the primary beam inputs received atoperation 505.

The beam pattern mixing unit 603 may apply the beam pattern matrix Z tothe N audio channels by multiplying the audio channel matrix X with thebeam pattern matrix Z as shown below:

${\begin{bmatrix}\alpha_{1,1} & \ldots & \alpha_{1,N} \\\vdots & \ddots & \vdots \\\alpha_{M,1} & \ldots & \alpha_{M,N}\end{bmatrix} \times \begin{bmatrix}x_{1} \\\vdots \\x_{N}\end{bmatrix}} = \begin{bmatrix}y_{1} \\\vdots \\y_{M}\end{bmatrix}$

Multiplication of the beam pattern matrix Z and the audio channel matrixX yields a basis or modal gain matrix Y, as shown in the above equation.This multiplication may be repeatedly performed for each sample periodof the N audio channels (each sample period having a new matrix X_(N))to yield a new modal gain matrix Y, for each sample period. Eachcomponent or value y in the modal gain matrix Y represents gainscorresponding to the N audio channels that will be transmitted tocorresponding modal filters 607 ₁-607 _(M), each of which represent acorresponding predefined modal beam pattern—see FIG. 6.

In one embodiment, prior to feeding the modal gain matrix Y to the modalfilters 607 ₁-607 _(M), operation 509 may mix orthogonal test signalsinto each modal beam pattern within the modal gain matrix Y, to generatean updated basis or modal gain matrix Y′. In some embodiments, theorthogonal test signals may be pseudorandom noise sequences, satisfyingone or more of the standard tests for statistical randomness. Forexample, the orthogonal test signals may be generated using a linearshift register. In this embodiment, taps of the shift register would beset differently for each of the M modal beam patterns, thus ensuringthat the M generated test signals are orthogonal to each other. In otherembodiments, the orthogonal test signals may be highly or nearlyorthogonal such that the dot product of each set of two orthogonal testsignals is close to zero (i.e., within a threshold or tolerance amountfrom zero). There may be M orthogonal test signals, which may be binarysequences, where, as noted above, M is the number of modal beampatterns. The orthogonal test signals may be variable in duration orlength (e.g., each may be 100 milliseconds to 3 seconds in duration).

Mixing may be performed at operation 509 using a mixer. The mixer 605may be composed of any set of elements that combine two or more signals.In one embodiment, the mixer 605 may include a resistor network, bufferamplifiers, transistors, diodes, and/or other related components. In oneembodiment, the modal/basis gain matrix Y may be combined with a matrixP of orthogonal test signals p₁, p₂, . . . p_(m) (or PSN₁, PSN₂, . . .PSN_(M) as depicted in FIG. 6 where PSN is an abbreviation forpseudo-random noise) as shown below, to generate an updated modal/basisgain matrix Y′:

${\begin{bmatrix}y_{1} \\\vdots \\y_{M}\end{bmatrix} + \begin{bmatrix}p_{1} \\\vdots \\p_{M}\end{bmatrix}} = \begin{bmatrix}y_{1}^{\prime} \\\vdots \\y_{M}^{\prime}\end{bmatrix}$

In the equation above, each of the modal gains y_(i) may be combinedwith corresponding orthogonal test signals p_(i) to yield an updatedmodal gain value y_(i)′ (forming a matrix Y′ that is composed of updatedmodal gain values.)

As noted above, following mixing of an orthogonal test signal with eachof the M modal gains at operation 509, the updated modal gain matrix Y′may be processed by corresponding modal/basis filters 607 at operation511, to produce a filtered modal/basis gain matrix. In one embodiment,each of the M modal filters 607 may compensate for radiationinefficiencies of sound at low frequencies, for each corresponding modalbeam pattern. In particular, higher order modal beam patterns (and/ormodal beam patterns with higher DI) may be more difficult to accuratelyproduce at lower frequencies, and requiring stronger drive signals(e.g., high voltage) to produce. Specifically, lower frequency soundstend to diffuse into the listening area 103 instead of forming directedpatterns. To compensate for these inefficiencies, the M modal filters607 may be linear digital filters that set their frequency responses toprovide the needed boost at low frequencies. For instance, a modalfilter 607 _(i) for a particular predefined modal beam pattern i mayboost the output power of its input signal below a roll-off or cut-offfrequency for the modal beam pattern i (e.g., the frequency at which thepower of the signal for the modal beam pattern has dropped by one-half).Compensating for inefficiencies in modal beam patterns allows the modalbeam patterns to be effectively and efficiently used at lowerfrequencies to produce more complex beam patterns (e.g., higher orderpatterns and/or beam patterns with higher directivity indices). In someembodiments, these M modal filters 607 may be affected by the diameterof the cabinet of the loudspeaker array 105. In particular, the farthestdistance between two of the transducers 107, e.g., two transducers thatare on opposing sides of the cabinet, which may be defined by a diameterof a circular cabinet, may affect the efficiencies and shape of soundproduced by sets of transducers 107. Thus, the settings for a particularmodal filter 607 i may be adjusted according to the dimensions of thecabinet.

Still referring to FIG. 6, in one embodiment, the modal filters 607 mayproduce a filtered basis/modal gain matrix that is also referred to hereas a matrix Q of modal amplitudes. The matrix Q may be processed by amodal decomposition unit 611, also referring now to operation 513 inFIG. 5, to produce the drive signals for each transducer 107 in thearray 105. The modal amplitude matrix Q may be represented as shownbelow:

$Q = \begin{bmatrix}q_{1} \\\vdots \\q_{M}\end{bmatrix}$

The modal decomposition unit 611 may determine how each transducer 107in the loudspeaker array 105 is to be driven, so that the array 105 as awhole produces each of the primary beams. For example, to produce anomnidirectional modal beam pattern, each of the transducers 107 in theloudspeaker array 105 may be driven using the same driving signal (norelative delays, no relative gain differences). In contrast, a dipolemodal beam pattern may require driving different sets of transducers 107with driving signals that have varied weights (to achieve relative delayand/or relative gain differences.) In one embodiment, the modaldecomposition unit 611 may include a modal decomposition matrix T thatincludes real numbers defining weights for each of the M modal beampatterns, that correspond to each of the D transducers 107 in theloudspeaker array 105. The modal decomposition matrix may be a matrix ofreal numbers representing assignment levels for each modal beam patternto each transducer in the loudspeaker array, such that the transducersin the loudspeaker array produce each of the predefined modal patternsbased on the weights represented in the beam pattern mixing matrix. Themodal decomposition matrix T may be represented as:

$T_{D,M} = \begin{bmatrix}\beta_{1,1} & \ldots & \beta_{1,M} \\\vdots & \ddots & \vdots \\\beta_{D,1} & \ldots & \beta_{D,M}\end{bmatrix}$

In this example matrix T, each column represents a predefined modal beampattern, while each row represents a transducer 107 in the loudspeakerarray 105. Each of the weights βi,j in the modal decomposition matrix Tmay be applied to the modal amplitudes q in the modal amplitude matrix Qto create drive signals for each transducer 107 in the loudspeaker array105. For example, the below sample modal decomposition matrix T definesweighting values for four modal beam patterns (four columns in thematrix) and eight transducers 107 (eight rows in the matrix) in aloudspeaker array 105:

$\quad\begin{bmatrix}1 & 0 & 1 & 1 \\\frac{1}{2} & 1 & 0 & 1 \\0 & 0 & {- 1} & 1 \\{- \frac{1}{2}} & {- 1} & 0 & 1 \\{- 1} & 0 & 1 & 1 \\{- \frac{1}{2}} & 1 & 0 & 1 \\0 & 0 & {- 1} & 1 \\\frac{1}{2} & {- 1} & 0 & 1\end{bmatrix}$

The weights β may be chosen to represent the arrangement of thetransducers 107 in the loudspeaker array 105. For example, as shown inFIGS. 1 and 3, the transducers 107 may be arranged in a circle aroundthe cylindrical cabinet of the loudspeaker array 105. To accommodate forthe positioning of the transducers 107 in a circle, the weights β thatare in each column of the matrix may correspond to different phases of asine or a cosine curve. In one embodiment, the weights β are set duringconfiguration of the audio emission device 101A. In another embodiment,the manufacturer of the audio emission device 101A may preset theweighting values β for one or more different types of listeningenvironments 103.

To generate a set of driving signals for the transducer 107,respectively, the modal amplitude matrix Q received from the modalfilters 607 may be multiplied with the modal decomposition matrix T asshown below:

${\begin{bmatrix}\beta_{1,1} & \ldots & \beta_{1,M} \\\vdots & \ddots & \vdots \\\beta_{D,1} & \ldots & \beta_{D,M}\end{bmatrix} \times \begin{bmatrix}q_{1} \\\vdots \\q_{M}\end{bmatrix}} = \begin{bmatrix}r_{1} \\\vdots \\r_{D}\end{bmatrix}$

The resulting driving signal matrix R includes a separate driving signalr_(i) for each of the D transducers 107. By multiplying the modalamplitude matrix Q with the modal decomposition matrix T, each of thedriving signals r_(i) includes a weighted component of each predefinedmodal beam pattern. In this manner, the transducers 107 may be driven toproduce the desired N primary beams, for the N audio channels, by usingappropriate components from each of the predefined, M modal beampatterns. And since the modal beam patterns also include respectiveorthogonal test signals, the modal beam patterns here may be used asaudio beacons, as will be described further below.

At operation 515, the driving signals r produced by the modaldecomposition unit 611 may be output to power amplifiers for drivingcorresponding transducers 107 in the loudspeaker array 105. Accordingly,the loudspeaker array 105 produces in the listening area 103 the primarybeam patterns, which have been defined by the beam inputs received atoperation 505, and in part as a result of the relative weights that wereapplied to the modal beam patterns by the decomposition unit 611. Sinceeach of the modal beam patterns effectively included injected orthogonaltest signals, these orthogonal test signals are also projected into thelistening area 103 (by the audio emission device 101A).

At operation 517, the audio capture device 101B may capture the soundthat is being produced by the audio emission device 101A (within thelistening area 103), using the sound detection unit 405 and themicrophones 109—see FIG. 4. The captured sound, represented in acaptured audio signal from one or more of the microphones 109, mayinclude sounds representing each of the modal beam patterns, whichcompose the primary beams. At operation 519, the captured audio signalmay be analyzed to determine the relative intensities of each of theorthogonal test signals (e.g., relative to each other or to an expected,predetermined reference level), in the captured audio signal. Therelative intensities of each of the orthogonal test signals in thecaptured audio signal may be used by the orientation determination unit407 to determine the positioning/orientation of the audio capture device101B relative to the audio emission device 101A at operation 519. Forexample, based on a knowledge of the modal beam patterns used by theaudio emission device 101A, operation 519 may determine the rotation(angular orientation) and distance of the audio capture device 101Brelative to the audio emission device 101A as shown in FIG. 9.

As discussed above, by injecting orthogonal test signals into a processin which modal beam patterns are used to generate primary audio beams,the modal beam patterns may effectively function as audio beacons. Inparticular, the orthogonal test signals may be detected by the audiocapture device 101B and analyzed to determine the relative position ofthe audio emission device 101A relative to the audio capture device101B. Accordingly, audio beacons that are separate from the primaryaudio beams do not need to be generated, as instead the modal beampatterns that form the primary audio beams may be used as audio beacons,for determining the relative position of the audio emission device 101Arelative to the audio capture device 101B.

As explained above, an embodiment of the invention may be an article ofmanufacture in which a machine-readable medium (such as microelectronicmemory) has stored thereon instructions which program one or more dataprocessing components (generically referred to here as a “processor”) toperform the operations described above including the digital signalprocessing tasks of the audio emission device recited in operations 507,509, 511, and 513 of FIG. 5. In other embodiments, some of theseoperations might be performed by specific hardware components thatcontain hardwired logic circuit blocks (e.g., dedicated digital filterblocks, state machines, and other combinational or sequential logiccircuits). Those operations might alternatively be performed by anycombination of programmed data processing components and fixed,hardwired logic circuit components.

While certain embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat the invention is not limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those of ordinary skill in the art. The description is thus tobe regarded as illustrative instead of limiting.

What is claimed is:
 1. A method for determining the spatial relationshipbetween an audio emission device and an audio capture device,comprising: applying weights to a plurality of predefined modal beampatterns, for each audio channel in a plurality of audio channels, toproduce a modal gain matrix representing a plurality of weighted modalbeam patterns, wherein the modal gain matrix represents the shapes of aplurality of primary beams in terms of the plurality of predefined modalbeam patterns; injecting a separate orthogonal test signal into each ofthe plurality of weighted modal beam patterns represented by the modalgain matrix; filtering the modal gain matrix that includes the injectedorthogonal test signals, by corresponding modal beam pattern filters;driving a loudspeaker array in the audio emission device to produce theprimary beams using the filtered modal gain matrix that includes theinjected orthogonal test signals; receiving a captured sound signalcorresponding to the primary beams detected by the audio capture device;and determining the spatial relationship of the audio capture devicerelative to the audio emission device based on intensities of theorthogonal test signals as extracted from the captured sound signal. 2.The method of claim 1, further comprising: processing the filtered modalgain matrix that includes the injected orthogonal test signals using amodal decomposition matrix to produce a set of drive signals used todrive individual transducers in the loudspeaker array to generate theprimary beams in terms of the plurality of predefined modal beampatterns, wherein the modal decomposition matrix is a matrix of realnumbers representing assignment levels for each predefined modal beampattern to each transducer in the loudspeaker array such that theloudspeaker array produces beams based on the weights applied to theplurality of predefined modal beam patterns.
 3. The method of claim 1,wherein each modal beam pattern filter corresponds to a separate modalbeam pattern in the plurality of predefined modal beam patterns, andeach modal beam pattern filter boosts a power level of a correspondingmodal gain in the modal gain matrix below a roll-off frequencyassociated with a corresponding modal beam pattern.
 4. The method ofclaim 1, wherein the modal gain matrix includes individual real numbercoefficients for each of the predefined modal beam patterns.
 5. Themethod of claim 1, wherein the orthogonal test signals satisfy one ormore of tests for statistical randomness.
 6. The method of claim 1,wherein the plurality of predefined modal beam patterns include avertical dipole pattern, a horizontal dipole pattern, and anomnidirectional pattern.
 7. A system, comprising: an audio emissiondevice, including: a matrix mixing unit to apply weights to a pluralityof predefined modal beam patterns, for each audio channel in a pluralityof audio channels, to produce a modal gain matrix representing aplurality of weighted modal beam patterns, wherein the modal gain matrixrepresents the shapes of a plurality of primary beams in terms of thepredefined modal beam patterns; a mixer to inject separate pseudorandomnoise sequences into each weighted modal beam pattern represented by themodal gain matrix; a plurality of modal beam pattern filters to filterthe modal gain matrix that includes the injected pseudorandom noisesequences; a loudspeaker array to produce the primary beams using thefiltered modal gain matrix that includes the injected pseudorandom noisesequences; and an audio capture device, including: a plurality ofmicrophones to detect sound corresponding to the primary beams, andgenerate a detected sound signal; and an orientation determination unitto determine the spatial relationship of the audio capture devicerelative to the audio emission device based on intensities of thepseudorandom noise sequences extracted from the detected sound signal.8. The system of claim 7, wherein the audio emission device furtherincludes: a modal decomposition unit to process the filtered modal gainmatrix that includes the injected pseudorandom noise sequences using amodal decomposition matrix to produce a set of drive signals used todrive individual transducers in the loudspeaker array to generate theprimary beams in terms of the predefined modal beam patterns, whereinthe modal decomposition matrix is a matrix of real numbers representingassignment levels for each predefined modal beam pattern to eachtransducer in the loudspeaker array such that the transducers in theloudspeaker array produce each of the predefined modal patterns based onthe applied weights.
 9. The system of claim 7, wherein each modal beampattern filter corresponds to a separate predefined modal beam patternin the plurality of predefined modal beam patterns and each modal beampattern filter boosts a power level of a corresponding modal gain in themodal gain matrix below a roll-off frequency associated with acorresponding predefined modal beam pattern.
 10. The system of claim 7,wherein the modal gain matrix includes individual real numbercoefficients for each of the predefined modal beam patterns.
 11. Thesystem of claim 7, wherein the pseudorandom noise sequences satisfy oneor more tests for statistical randomness.
 12. The system of claim 7,wherein the predefined modal beam patterns include a vertical dipolepattern, a horizontal dipole pattern, and an omnidirectional pattern.13. An article of manufacture, comprising: a non-transitorymachine-readable storage medium that stores instructions which, whenexecuted by a processor in a computing device, apply weights to aplurality of modal beam patterns for each audio channel in a set ofaudio channels to produce a modal gain matrix representing weightedmodal beam patterns, wherein the modal gain matrix represents the shapeof a primary beam in terms of the modal beam patterns, wherein theprimary beam is to contain content from one or more of the audiochannels; inject separate orthogonal test signals into each modal beampattern represented by the modal gain matrix; filter the modal gainmatrix that includes the injected orthogonal test signals bycorresponding modal beam pattern filters; drive a loudspeaker array inan audio emission device to produce the primary beam using the filteredmodal gain matrix that includes the injected orthogonal test signals;generate a captured audio signal that corresponds to the primary beambased on sound captured by an audio capture device; and determine thespatial relationship of the audio capture device relative to the audioemission device based on intensities of the orthogonal test signalsextracted from the captured audio signal.
 14. The article of manufactureof claim 13, wherein the non-transitory machine-readable storage mediumincludes further instruction that when executed by the processor:process the filtered modal gain matrix that includes the injectedorthogonal test signals using a modal decomposition matrix to produce aset of drive signals used to drive individual transducers in theloudspeaker array to generate the primary beam in terms of the modalbeam patterns, wherein the modal decomposition matrix is a matrix ofreal numbers representing assignment levels for each modal beam patternto each transducer in the loudspeaker array such that the transducers inthe loudspeaker array produce each of the modal beam patterns based onthe applied weights.
 15. The article of manufacture of claim 13, whereineach modal beam pattern filter corresponds to a separate modal beampattern in the plurality of modal beam patterns and each modal beampattern filter boosts a power level of a corresponding modal gain in themodal gain matrix below a roll-off frequency associated with acorresponding modal beam pattern.
 16. The article of manufacture ofclaim 13, wherein the modal gain matrix includes individual real numbercoefficients for each of the modal beam patterns.
 17. The article ofmanufacture of claim 13, wherein the orthogonal test signals satisfy oneor more tests for statistical randomness.
 18. An audio emission device,comprising: a matrix mixing unit to apply weights to a plurality ofpredefined modal beam patterns, for each audio channel in a plurality ofaudio channels, to produce a modal gain matrix representing a pluralityof weighted modal beam patterns, wherein the modal gain matrixrepresents the shapes of a plurality of primary beams in terms of thepredefined modal beam patterns; a mixer to inject separate pseudorandomnoise sequences into each weighted modal beam pattern represented by themodal gain matrix; a plurality of modal beam pattern filters to filterthe modal gain matrix that includes the injected pseudorandom noisesequences; a loudspeaker array to produce the primary beams using thefiltered modal gain matrix that includes the injected pseudorandom noisesequences; a communications interface to receive a detected sound signalgenerated by an audio capture device configured to detect soundcorresponding to the primary beams using a plurality of microphones; andan orientation determination unit to determine the spatial relationshipof the audio capture device relative to the audio emission device basedon intensities of the pseudorandom noise sequences extracted from thedetected sound signal.
 19. The audio emission device of claim 18,further including: a modal decomposition unit to process the filteredmodal gain matrix that includes the injected pseudorandom noisesequences using a modal decomposition matrix to produce a set of drivesignals used to drive individual transducers in the loudspeaker array togenerate the primary beams in terms of the predefined modal beampatterns, wherein the modal decomposition matrix is a matrix of realnumbers representing assignment levels for each predefined modal beampattern to each transducer in the loudspeaker array such that thetransducers in the loudspeaker array produce each of the predefinedmodal patterns based on the applied weights.
 20. The audio emissiondevice of claim 18, wherein each modal beam pattern filter correspondsto a separate predefined modal beam pattern in the plurality ofpredefined modal beam patterns and each modal beam pattern filter boostsa power level of a corresponding modal gain in the modal gain matrixbelow a roll-off frequency associated with a corresponding predefinedmodal beam pattern.
 21. The audio emission device of claim 18, whereinthe modal gain matrix includes individual real number coefficients foreach of the predefined modal beam patterns.
 22. The audio emissiondevice of claim 18, wherein the pseudorandom noise sequences satisfy oneor more tests for statistical randomness.
 23. The audio emission deviceof claim 18, wherein the predefined modal beam patterns include avertical dipole pattern, a horizontal dipole pattern, and anomnidirectional pattern.
 24. An audio capture device, comprising: amatrix mixing unit to apply weights to a plurality of predefined modalbeam patterns, for each audio channel in a plurality of audio channels,to produce a modal gain matrix representing a plurality of weightedmodal beam patterns, wherein the modal gain matrix represents the shapesof a plurality of primary beams in terms of the predefined modal beampatterns; a mixer to inject separate pseudorandom noise sequences intoeach weighted modal beam pattern represented by the modal gain matrix; aplurality of modal beam pattern filters to filter the modal gain matrixthat includes the injected pseudorandom noise sequences; acommunications interface to transmit the primary beams to an audioemission device configured to produce the primary beams with aloudspeaker array, the primary beams using the filtered modal gainmatrix that includes the injected pseudorandom noise sequences; aplurality of microphones to detect sound corresponding to the primarybeams, and generate a detected sound signal; and an orientationdetermination unit to determine the spatial relationship of the audiocapture device relative to the audio emission device based onintensities of the pseudorandom noise sequences extracted from thedetected sound signal.
 25. The audio capture device of claim 24, furtherincluding: a modal decomposition unit to process the filtered modal gainmatrix that includes the injected pseudorandom noise sequences using amodal decomposition matrix to produce a set of drive signals used todrive individual transducers in the loudspeaker array to generate theprimary beams in terms of the predefined modal beam patterns, whereinthe modal decomposition matrix is a matrix of real numbers representingassignment levels for each predefined modal beam pattern to eachtransducer in the loudspeaker array such that the transducers in theloudspeaker array produce each of the predefined modal patterns based onthe applied weights.
 26. The audio capture device of claim 24, whereineach modal beam pattern filter corresponds to a separate predefinedmodal beam pattern in the plurality of predefined modal beam patternsand each modal beam pattern filter boosts a power level of acorresponding modal gain in the modal gain matrix below a roll-offfrequency associated with a corresponding predefined modal beam pattern.27. The audio capture device of claim 24, wherein the modal gain matrixincludes individual real number coefficients for each of the predefinedmodal beam patterns.
 28. The audio capture device of claim 24, whereinthe pseudorandom noise sequences satisfy one or more tests forstatistical randomness.
 29. The audio capture device of claim 24,wherein the predefined modal beam patterns include a vertical dipolepattern, a horizontal dipole pattern, and an omnidirectional pattern.